Alternating-current-motor starter



Sept. 15, 1925 W. E. PAUL \ALTERNATING CURRENT MOTOR STARTER Filed April26, 1924 (L N, start/n9 0 ,2 22 o i /9 1 L I runn/ng 5 {@J /4 runningstar ting starting Inventor:

WHliam E. Paui,

y- M His Attorney."

Patented Sept. 15.1925;

UNITED STATES.

WILLIAM E. PAUL, OF SCHENECTADY, NEW YORK, ASSIGNOB 'IO GENERAL ELECTRICPATENT. OFFICE.

COMPANY, A CORPORATION OF NEW YORK.

Application filed April 26, 1924. Serial No. 709,302.

To all whom it'may concern:

Be it known that I, WILLIAM E. PAUL, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements inAlternating-Current-Motor Starters, of which the following is aspecification.

My invention relates to improvements in alternating current motorstarters of the compensator type employing separately operable startingand running switch contact mechanism.

One of the objects of the invention is to provide a simple and effectivearrangement involving a starting switch and a separatel operable runningswitch in connection Wit a starting auto-transformer, with theconnections arranged in such a manner that the motor circuit will not beopened during the starting interval and the motor will be connecteddirectly to the source of sup ly through the starting and runningswitclies for the normal runnin of the motor.

A further object of the invention is to pro vide an arrangement of thecharacter indicated whereby two substantially similar plural poleswitches may be employed, preferably two normally open substantiallysimilar oil switches, one switch serving as a starting switch and theother'switch serving as a running switch, together with connec-' tionswhereby the neutral of the auto-transformer is closed by contactmechanism of the running switch when the running switch is in the openposition, the neutral is opened in the closed position of the runningswitch so that the motor is connected to the line through the taps ofthe auto-transformer when the starting switch is closed, theautotransformer serves as a reactor while the running switch is beingclosed, and the motor is connected directly to the line when bothswitches are closed.

A further object of the invention is to provide interlocking connectionsbetween the starting and rurming switches to prevent closing thestarting switch unless the running switch is in the open position, so asto prevent connecting the motor directly to the line without employingthe auto-transformer to s pply a red ced p ential for startin These andother objects of the invention A ployed in the system of Fig. 1, only somuch of the structural features of the contact mechanism and theoperating means therefor being shown as would seem necessary to anunderstanding of the invention, and Fig. 3 is an end view of thestarting and running oil switch mechanism shown in Fig. 2.

Referring to the drawing, the electric motor 10 of the alternatingcurrent type is ar-' ranged to be started from the three phasealternating current source of supply 11, by means of the starting switch12 in cooperation with the starting auto-transformer 13 and the runningswitch 14. The starting switch, the running switch and theautotransformer are connected in such a way that the closing of thestarting switch will connect the motor to the source through thestarting taps of the auto-transformer 13 and when the motor has come upto speed, the closing of the running switch 14 will connect the motordirectly to the supply circuit.

The switches 12 and 14 are substantially similar switches, each havingthree circuit making movable contact members corresponding to the numberof phases of the source of supply. As shown, the switches are of thefour pole type, although the switch 12 is not provided with the fourthcircuit making contact member, since this member is unnecessary, itbeing sufiicient to merely retain at least one of the pole terminals ofthe switch 12 for use in closing the neutral of the auto-transformer incooperation with the fourth circuit makin contact member 15 of therunning switc This contact member 15 of the running switch is arrangedso as to be in the closed position normally while the other threecontact members of the running switch are arranged to be in theirrespective open positions normally. The circuit making contact membersof the starting switch are also arranged to be in their respective openpositions normally. The conductors 16,.17 and 18 are provided forinterconnecting corresponding pole terminals of the starting and therunning switches, as shown, and the terminals of thestartingauto-transformer are connected to these conductors respectively.The neutral of the auto-transformer is formed by attaching two of theother terminals of the auto-transformer to the pole terminals 19 and 20associated with the fourth contact member 15 of the running switch. Theconnection from the remaining coil of th e auto-transformer is made tothe pole terminals 21 associated with the running switch and theflexible jumper 22 is connected between the pole terminals 21 and thecontact member 15 so that with the running switch in the open positionthe neutral of the autotransformer will be closed. Conductors 23, 24 and25 permanently connect the taps of the starting auto-transformer withthe motor. I

In order to prevent closing the starting switch unless the runningswitch is in the open position, I have provided a mechanicalinterlocking member 26 which cooperates with a cam surface 27 of therunning switch and a pivotly mounted biased detent 28 connected with thestarting switch.

By reference to Figs. 2 and 3 it will'be seen that the switches which Iprefer to use are of the oil switch type, and in these figures only somuch of the oil switch is shown as is necessary for the understanding ofthe invention. By reference to Fig. 2 it will be seen that I haveprovided the ordinary form of four pole oil switch with an arrangementwhereby the circuit making contact member 15 makes engagement with itsrespective pole terminals in the open position of the switch, while theother contact members of the switch are out of engagement with theirrespective pole terminals. The flexible jumper 22 connects the poleterminal 21 of the starting switch (Fig. 3)

and this jumper is connected to the circuit making contact member 15' ofthe running switch by any suitable means such as the clamp 29. Byreference. to Fig. 3, it will be seen vthat the interlocking connectionbetween the starting and the running switches is conveniently-mounted onthe casing of the switches and cooperates with movable parts oftheoperating mechanism of the switches so as to provide the protectionheretofore referred to.

As thus constructed and' arranged and with the, parts in theirrespective positions shown inthe drawings, the operation of my inventionis as follows:

In order to start the motor, the starting switch 12 will be firstclosed, thereby connecting the motor to the source 11 throtigh thestarting auto-transformer 13 which serves as a step-downauto-transformer to apply a reduced potential to the motor for starting,because of the fact/that the neutral of the auto-transformer is closedthrough the running switch is in the open position.

When the motor has come up to a proper speed on the starting taps of theauto-transformer, the running switch 14 is closed. It

will be observed that during the intervalof closing the running switchthe neutral of the auto-transformer is opened by reason of the fact thatthe circuit making contact 15 of the running switch will open thecircuit through its contacts. However, this will not effect aninterruption of the cur rent being supplied to the motor, since duringthis interval the motor will receive energy, through the startingauto-transformer serving as a reactor. This prevents a drop in speed andtorque of the motor during the transition from the startingto the fullrunning position. When the running switch is closed the motor isconnected directly to the source of supply through the starting and therunning switches.

If the starting switch is opened so as to disconnect the motor from thesource of supply and stop the motor, the starting switch cannot bethereafter again closed unless the running switch is also returned tothe open position. The interlocking member 26 is shifted by means of thecam 27 of the running switch so as to be in engagement with the pivoteddetent of the starting switch, but when the running switch is in theopen position the interlocking member 26 is returned to the positionshown in the drawing by means of the biasing spring 30. It will also beobserved that the interlocking member 26 does not interfere with theopening of the starting switch after the running switch is closed,because of the fact that the detent 28 will move about its pivotedconnection with the starting switch against the action of its biasingspring.

The arrangement above set forth provides a very simple and effectivemeans-whereby two substantially similar switches may be employed forconnecting the motor to the supply circuitand whereby an'operation ofthe switches which. would likely cause injury to the motor is prevented.It will also be noted that the connection of the source of supply to themotor is maintained throughout the starting interval so that the speedand torque of the motor will not drop as in former arrangements in whichthe starting switch is opened prior to closing the running switch. Ifthe running switch is opened after the motor is connected directly tothe source, no damage results and although ordinarily it is notdesirable to do this, however, under certain conditions it is desirableto have this feature in order to obtain temporarily a reduced speedwithout the necessity of first opening the starting switch. Thereduction in the motor speed will be brought about, particularly if themotor is running under load, because tap voltage is applied to themotor, but it is to be noted that auto-transformers are ordinarily notdesigned for continuous running on the taps of the auto-transformer.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is: 1; A starter for polyphase alternating current motors,comprising a starting autotransformer, a starting switch having a set ofnormally open circuit making contact members corresponding to the phasesof the' source of supply and an additional set of terminals, a runningswitch having a set of normally open circuit making contact memberscorresponding to the phases of the said source and an additional movablecontact member arranged to be in the closed position normally, aflexible jumper from one of said terminals of the starting switch to thesaid additional contact member of the running switch for closing theneutral of the auto-transformer in the open position of the runningswitch, and connections whereby closing the starting switch connects themotor to the source of supply through the starting taps of theauto-transformer, subsequently operating the running switch toward theclosed position opens the neutral of the auto-transformer so that themotor is connected to the source through the auto-transformer serving asa reactor during the interval of closing the running switch, and themotor is connected directly to the source through the starting andrunning switches when the running switch closes.

2. A starter for polypha'se alternating current motors, comprising astarting autotransformer, a normally open starting switch having atleast one extra pole more than the number of conductors of the supp-1ycircuit, a normally open running switch having a number of poles similarto the starting switch, conductors interconnecting correspondingterminals of the said switches through which the motor is supplied withcurrent from the supply circuit, connections between one set ofterminals of the auto transformer to the respective conductors bebeingclosed in the open osition of the a running switch by means 0 a flexibleconnection from a terminal of the extra poie of the starting switch tothe extra contact mem ber of the running switch, whereby the motor isconnected to the source of supply through the starting taps of theauto-transformer by the closing of said starting switch,

the neutral of said auto-transformer is opened by the said contactmember so that the motor is connected to the source through theauto-transformer serving as a reactor during the interval of closing therunning switch, and the'motor is connected directly tothe source throughthe running is closed.

3. A starter. for three phase alternating current motors, comprising twonormally open four pole switches having each three contact members forconnecting the motor to a source of supply, one of said switches being astarting switch and the other being a running switch, a startingauto-transformer having one set of terminals of the said starting andauto-transformer connected to respective conductors between the saidswitches, the neutral of the auto-transformer being normally closed withthe running switch in the open position by means of a connection fromone terminal of the auto-transformer to the fourth contact member of therunning switch and connections from the other terminals of theauto-transformer to the pole terminals of the said fourth contact member of the running switch, the starting taps of the auto-transformerbeing permanently connected to the motor, whereby closing the startingswitch connects the motor to the source through the starting taps of theautotransformer, the neutral of the auto-transformer is opened byclosing the running switch thus causing the auto-transformer to serve asa reactor during the interval of closing, and the closing of the runningswitch connects the motor directly to the source through the startingswitch.

4. A starter for polyphase alternating cur- .rent motors, comprising astarting autotransformer, a normally open starting switch, a normallyopen running switch arranged to close the neutral of theauto-transformer in the open position thereof, interlocking connectionsbetween the said switches for preventing the closing of the startingswitch unless the running switch is open, and. connections wherebyclosing the starting switch connects the motor to the source through thestarting tips of the autotransformer, operating the running switchtoward the closed osition opens the neutral of the auto-trans ormer sothat the motor is connected to the source through the autotransformerserving as a reactor during the interval of closing the running switch,and.

the motor is connected directly to the source through the starting andrunning switches when the running switch closes, 10

In witness whereof, I have hereunto set my hand this 25th day of April,19%.

WILLIAM E. PAUL.

